The present invention relates to an electromagnetic pump, and more particularly to an electromagnetic pump for use in a pressure-feed device for supplying molten metal to a casting machine or the like.
One conventional pressure-feed device employing an electromagnetic pump is illustrated in FIGS. 1 and 2 of the accompanying drawings.
The conventional pressure-feed device includes a fixed furnace 2 for holding molten metal, and a supply pipe system coupled to the furnace 2 and comprising a horizontal duct 4 heated to a high temperature, a coupling 6, a vertical duct 8, an elbow 10, and a nozzle 12 with a mouthpiece 14 connected thereto. The vertical duct 8, the nozzle 12, and the mouthpiece 14 are each swingable. The components of the supply pipe system are joined through spherical surfaces to compensate for heat-induced elongation, the spherical surfaces being sealed by heat-resistant gaskets.
A coil 16 is disposed around the duct 4. As shown in FIG. 2, a core protection tube 18 is fixed to and horizontally supported on one end of the coupling 6, and extends coaxially into the duct 4. The core protection tube 18 and the duct 4 define a space 20 therebetween. A core 22 made of a magnetic material is horizontally supported in the core protection tube 18 by means of a core holder 26 with one end thereof secured to a support plate 24 attached to the core protection tube 18.
When an electric current is passed through the coil 16 to produce a moving magnetic field, molten metal filled in the space 20 is supplied through the supply pipe system to the mouthpiece 14.
FIGS. 3 and 4 illustrate another conventional pressure-feed device. Those parts shown in FIGS. 3 and 4 which are identical or correspond to those shown in FIGS. 1 and 2 are denoted by identical reference numerals, and will not be described in detail.
The pressure-feed device shown in FIGS. 3 and 4 includes a furnace 28 movable in the directions of the arrow A by a cylinder 30. A duct 32 and a nozzle 34 which are connected to the furnace 28 are horizontally aligned with each other. As shown in FIG. 4, the nozzle 34 and the duct 32 are interconnected by a coupling 36 of ceramic having a molten metal passage 36a defined therein and a core protection tube 38. The core protection tube 38 has a protective tube member 38a supported horizontally in the duct 32 with a space 40 defined between the inner peripheral wall surface of the duct 32 and the protective tube member 38a. A core 22 is horizontally supported in the protective tube member 38a by the core holder 42.
When the coil 16 of FIGS. 3 and 4 is energized, molten metal from the furnace 28 is fed through the duct 32 and the nozzle 34 to the mouthpiece 14.
In the conventional electromagnetic pumps shown in FIGS. 1 through 4, the cores 22 are protected from erosion by the core protection tubes 18, 38. The electromagnetic pump illustrated in FIG. 1 is made up of many parts, and includes a total of seven sealed regions where the joined ends of the parts are sealed. Since the furnace 2 and the mouthpiece 14 are fixed in position, it is quite difficult to assemble the electromagnetic pump of FIGS. 1 and 2. Moreover, the electromagnetic pump tends to suffer molten metal leakage due to possible errors in assembly.
The electromagnetic pump shown in FIGS. 3 and 4 has a fewer number of sealing regions since it only requires five regions to be sealed. However, the electromagnetic pump is very expensive to manufacture because the coupling 36 and the core protection tube 38 have molten metal passages that must be carefully manufactured through complex machining processes.